Proportional radiation counters (PCs) rely upon a sealed gas-filled device with an electrical potential applied across the gas in which a penetrating radiation, such as gamma rays or neutrons, penetrate the outer PC structure and ionize fill gas molecules. Other PCs operate in a “flow-through” mode where the sample is introduced into the interior of the PC to allow for the analysis of low-penetrating radiation such as beta particles. In this mode, however, PCs are highly accurate, but are limited as to materials that can be analyzed. PCs are designed to operate in a pulse mode and depend upon gas multiplication to amplify the charge from the ion pair created by ionizing radiation in the gas phase. The generated pulse is proportional to the energy of the radiation and is a basis for radiation spectroscopy.
PCs are comprised of an anode and a cathode, with the cathode often forming part of the outer PC structure. The ionized gas, present as electrons or free radicals, is collected as an electrical charge at the anode. Typically, a PC is filled with a noble gas or a noble gas containing mixture which limits free radical quenching. Gas multiplication is the result of increasing the electrical field within the PC to a sufficiently high value such that the ionized radical interacts with the fill gas causing a secondary ionization. This results in a cascade of ionization events, forming an electron avalanche that is detected at the anode in a process very similar to a photoionization (i.e., photomultiplier) detector. This signal amplification is the basis for the detection of conventional PC designs.
One limitation of conventional PCs is the reliance on high stable voltage sources used to produce the electric field required to reach the proportional counting region. The high voltage requirements have been a limitation for portable and remotely deployable PCs. While step-up transformers can increase the voltage needed for portable PCs, this process inherently adds noise to the measurement and reduces measurement sensitivity. In addition, there still remains a need for detection devices which are portable, have a high detection efficiency, operate on portable power supplies for extended periods of time, and exhibit a smaller electromagnetic field signal. Accordingly, there is room for variation and improvement in the art.